Composition of baths for electrodeposition of bright zinc

ABSTRACT

IT HAS BEEN FOUND THAT THE ADDITION OF THE EPIHALOHYDRIN QUATERNARY SALT OF AMINATED POLYEPICHLOROHYDRIN TO AQUEOUS, ALKALINE ELECTROPLATING BATHS CONTAINING ZINC IONS, PROVIDES SMOOTH, BRIGHT DEPSITS OF ZINC.

United States Patent 3,824,158 COMPOSITION OF BATHS FOR ELECTRODEPOSI- TION 0F BRIGHT ZINC William E. Rosenberg, Par-ma, Ohio, assignor to R. 0. Hull 8: Company, Inc., Cleveland, Ohio No Drawing. Filed Jan. 26, 1973, Ser. No. 327,016 Int. Cl. *C23b 5/10, 5/46 U.S. Cl. 204-55 R 6 Claims ABSTRACT OF THE DISCLOSURE It has been found that the addition of the epihalohydrin quaternary salt of aminated polyepichlorohydrin to aqueous, alkaline electroplating baths containing zinc ions, provides smooth, bright deposits of zinc.

BACKGROUND OF THE INVEN'I ION This invention pertains to improvements in the electrodeposition of zinc from aqueous, alkaline plating baths.

Within the past few years, considerable attention has been drawn toward improving the environment. 0f great concern to the electroplater is water pollution from the rinse waters of plating operations. Zinc plating in the past was quite successfully achieved by utilizing electroplating baths which contained up to 120 gms. of sodium cyanide per liter. The rinse waters from a plating operation using this type of bath are of course quite toxic and it is no longer allowable to simply mix them with ordinary sewage. Effective, but expensive methods have been devised to detoxify these rinse waters, but costs of equipment and chemicals tend to make them quite uneconomical.

Aqueous, alkaline zinc plating baths that contain little or no sodium cyanide produce electrodeposits that are rough and spongy and completely unacceptable for just about any application. Recently, organic additives have been developed which, when included in a cyanide-free plating bath, do provide electrodeposits of fair quality. The overall brightness, range of allowable current-densities, and ductility of plate have been quite limited and improvements in these areas are greatly desired.

With this invention, the electroplating of brilliant deposits of zinc can be achieved without the use of toxic sodium cyanide. In addition to this the deposits are extremely ductile and a very wide range of allowable current densities is provided. These improvements have provided a novel, practical method of producing bright electrodeposits, of zinc from sodium cyanide-free electroplating baths.

SUMMARY OF THE INVENTION The present invention comprises an aqueous, alkaline electroplating bath, for producing a bright, lustrous, electrodeposit of zinc, containing zinc ions, and dissolved therein at a concentration of about 0.01 to about 10 gms. per liter, the epihalohydrin quaternary salt of aminated polyepichlorohydrin.

The invention is also an aqueous addition agent for aqueous, alkaline zinc electroplating baths, consisting essentially of from about 1 to 99 percent by weight of the gpgialohydrin. Quaternary salt of aminated polyepichloroy rin.

DETAILED DESCRIPTION Before amination and reaction with epihalohydrin :the

polyep'ichlorohydrin has the following general structure:

where n is about 10 to about 200. Epichlorohydrin polymers of various molecular weights are currently available in commerce and the technology for their preparation is extensively divulged in numerous papers and articles found in the chemical literature.

*Amination of polyepichlorohydrin to obtain a tertiary amine is accomplished by carefully heating stoichiometric quantities of a secondary amine and polyepichlorohydrin at temperatures ranging from 120 C. to 150 C. for at least 1 hour with good stirring. In the case where a highly volatile amine is used, the reaction must be carried out in a suitable vessel under pressure in order to obtain the required temperatures and avoid losing a low boiling reactant.

The aminated polyepichlorohydrin of this invention has the following general structure:

R+ 01- where R is the secondary aliphatic or alicyclic amine used to form a tertiary amine with polyepichlorohydrin.

Listed in Table I are the secondary aliphatic and alicyclic amines which form a part of this invention.

TA'BLE 1 Secondary Alicyclic and Secondary Aliphatic Amines Amination of Polyepichlorohydrin With Diethanol-amine Add 21 gms. diethanolamine to 18.6 gms. of polyepichlorohydrin in a vessel equipped with a reflux condenser. Heat to P40" C. with stirring and hold at this temperatur: for 1 hour. Cool reaction and dilute to 100 ml. with wa er.

Yield=% conversion to tertiary amine.

EXAMPLE llI Amination of Polyepichlorohydrin With N-Methyl Ethanolamine Add 15 gms. of N-methyl ethanolamine to 18.6 gms. of polyepichlorohydrin in a vessel equipped with a reflux condenser. Heat to 150 C. with stirring and hold at this temperature for 1 hour. Cool and dilute to ml. with water.

Yield=95% conversion to tertiary amine.

The reaction of epihalohydrins with tertiary amines derived from polyepichlorohydrin results in what is believed to be a quaternary amine in which the epoxide group or ring opened group plays an important role in the products activity as a brightening agent. The epihalohydrins that are used are epichlorohydrin and epibromohydrin. When other quaternizing agents are used in place of the epihalohydrins no similar brightening activity is observed. The quaternizing agents used were sodium-chloroacetate, allyl bromide, benzyl chloride, and 1-chloro-2,3 propanediol. It is important to add enough sodium hydroxide to neutralize the hydrochloric acid formed during the amination of polyepichlorohydrin before quaternization with epihalohydrin. It is not necessary to completely aminate the polyepichlorohydrin. Good results were obtained when only 50% conversion to the tertiary amine was attained.

If in fact the reaction of epihalohydrin and the animated polyepichlorohydrin forms something more complex than a quaternary salt it is not known. It is quite beyond the scope of this invention to speculate on the difficult to determine chemical bonding, hence the reaction product is simply called a quaternary salt.

EXAMPLE III Quaternization of Aminated Polyepichlorohydrin With Epichlorohydrin To the 100 ml. of solution from Example I add 6 grns. of sodium hydroxide and stir. Add 14 gms. of epichlorohydrin and heat to reflux with stirring. Hold at reflux for one hour and cool. This solution is the active addition agent.

EXAMPLE IV Quaternization of Aminated Polyepichlorohydrin With Epibromohydrin To 100 ml. of solution from Example II add 7.6 grns. of sodium hydroxide and stir. Add 26 gms. of epibromohydrin and heat to reflux with stirring. Hold at reflux for one hour and cool.

All testing was done in a conventional 267 ml. Hull Cell using steel panels and a zinc anode. Panels were plated at 2 amperes for minutes at a temperature of 80 F. In every case the epihalohydrin quaternary reaction product was compared to the unquaternized aminated polyepichlorohydrin and the aminated polyepichlorohydrin quaternized with allyl bromide, benzyl chloride, sodium chloroacetate, and 1-chloro-2,3-propanediol.

In all tests the epihalohydrin quaternary salts of aminated polyepichlorohydrin showed good brightening from about 0 to over 120 amps per square foot making them quite useful as brightening additives for commercial plating. In the comparative tests using the unquaternized aminated polyepichlorohydrins and the aminated polyepichlorohydrins that were quaternized but not with an epihalohydrin, the electrodeposits produced were extremely coarse and dull at current densities over 30 amps per square foot and either dull or only semibright at current densities below 30 amps per square foot.

The quaternary salts of this invention may be used in combination with any of the widely used brightening agents, eg gelatin, anisaldehyde, piperonal, veratraldehyde, 3-substituted-N-alkyl-pyridinium halide, and quaternary amines other than those of this invention. The brightening compositions of this invention are preferably used in the form of aqueous addition agents and contain from about 1 to 99% by weight of the epihalohydrin quaternary salt.

While the addition agents of this invention are eflective in many aqueous, alkaline zinc plating bath formulations, it is preferred to use any of the basic baths described in the following examples. It will be understood that the following examples are just illustrations and are not meant to limit the use of the invention to these bath compositions only.

EXAMPLE V Bath composition: Concentration in gms./liter Zinc oxide 9 Sodium hydroxide 75 2 molar solution of epichlorohydrin quaternary salt of polyepichlorohydrin aminated with dimethyl amine 5 EXAMPLE VI Bath composition: Concentration in gms./liter Zinc oxide 9 Sodium hydroxide 75 2 molar solution of epibromohydrin quaternary salt of polyepichlorohydrin aminated with N- The molarity of solution of epihalohydrin quaternary salt is based on the moles of secondary amine used in the amination step.

Having thus described this invention in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains to make and use the same, and having set forth the best mode contemplated of carrying out this invention, I state that the subject matter which I regard as being my invention is particularly pointed out and distinctly claimed in What is claimed, it being understood that equivalents or modifications of, or substitutions for, parts of the above specifically described embodiment of the invention may be made without departing from the scope of the invention as set forth in what is claimed.

What is claimed is:

1. An aqueous, alkaline, electroplating bath for producing a bright, lustrous electrodeposit of zinc, containing zinc ions, and dissolved therein between about 2 and about 5 gms./liter of the epihalohydrin quaternary salt of aminated polyepichlorohydrin which is prepared by first reacting stoichiometric amounts of polyepichlorohydrin with an amine from the group consisting of secondary aliphatic and secondary alicyclic amines at a temperature of about C. to C. for about one hour to form a polytertiary amine, then, after neutralization with alkali, reacting the polytertiary amine with an equimolar amount of epihalohydrin in an aqueous solution at about one molar concentration based on the moles of secondary amine used in the amination step, at reflux temperature for about one hour.

2. A bath composition as set forth in Claim 1 wherein the epihalohydrin is epichlorohydrin.

3. A bath composition as set forth in Claim 1 wherein the aliphatic secondary amine is dimethylamine.

4. A bath composition as set forth in Claim 1 wherein the aliphatic secondary amine is N-methyl ethanolamine.

5. A bath composition as set forth in Claim 1 wherein the alicyclic secondary amine is morpholine.

6. A bath composition as set forth in Claim 1 wherein there is present at least one of the substances selected from the group consisting of gelatin, anisaldehyde, piperonal, veratraldehyde, N-alkyl-3-carboxypyridinium halide, N- alkyl-3-carboxy alkyl pyridinium halide, and N-alkyl-3- carboxamido pyridinium halide.

(References on following page) 5 6 References Cited FOREIGN PATENTS UNITED STATES PA EN 1,910,466 9/ 1970 Germany 204-55 R 10/1948 Bair et 204-55 Y GERALD L. KAPLAN, Primary Examiner 1/1966 Burnson 20455 Y X 5 5/1957 Winters 204-55 Y US. Cl. X.R. 11/1958 Jackson 204-55 Y 204-Dig. 2 

